Most vehicles are provided with headlights and taillights, which are turned on when the vehicles move in the nighttime or in a dim or dark environment so as to serve as lighting and warning devices to ensure the safety in driving.
To further ensure the safety in driving, there are car manufacturers and users who mount light-emitting devices on two lateral sides of the vehicles, such as on vehicle wheels, to emit light thereat. The light-emitting devices provided on the vehicle wheels also provide an ornamental effect.
The conventional light-emitting device for vehicle wheel is manually controlled. That is, a driver has to turn on a switch of the light-emitting device for the latter to emit light; and to turn off the switch when it is not necessary to use the light-emitting device. It is troublesome to turn on or off the light-emitting device. Moreover, it is possible the driver does not timely turn on or off the light-emitting device due to negligence, thereby either adversely affecting the safety in driving or unnecessarily waste battery power supplied to the light-emitting device.
U.S. Pat. No. 6,572,251, entitled “Light Emitting Assembly for Vehicle Wheel” granted to the same inventor of the present invention, discloses a light emitting assembly that is mounted on a vehicle wheel to automatically emit light when the vehicle wheel rotates, and to automatically turnoff light emitting when the vehicle wheel stops rotating. The light emitting assembly for vehicle wheel disclosed in U.S. Pat. No. 6,572,251 includes a casing, a circuit board, a lead frame, and an elastic metal contact member.
The casing is provided at an end with a receiving open chamber, in which a battery cell is mounted. The circuit board is disposed on the receiving open chamber of the casing, and provided on one side thereof with a light-emitting device, and at radially inner and outer areas on the other side thereof facing toward the receiving open chamber with first and second annular metal contacts, respectively. The light-emitting device has two electrodes separately electrically connected to the first and second annular metal contacts, and the second annular metal contact is electrically connected to one of two poles of the battery cell via the casing. The lead frame is mounted in the receiving open chamber and located between the first and the second annular metal contact with an end electrically connected to the other pole of the battery cell. The elastic metal contact member has an end fixed to the circuit board and electrically connected to the first annular metal contact. When the vehicle wheel rotates, the elastic metal contact member is biased by a centrifugal force to contact with the lead frame and thereby closes the circuit between the battery cell and the light-emitting device, allowing the latter to emit light. And, when the vehicle wheel stop rotating, the elastic metal contact member restores to its home position without contacting with the lead frame and thereby opens the circuit between the battery cell and the light-emitting device, preventing the latter from emitting light. That is, the light-emitting device automatically emits light or turns off light emitting when the vehicle wheel rotates or stops, respectively. Therefore, the light emitting assembly for vehicle wheel disclosed in U.S. Pat. No. 6,572,251 is convenient for use and effectively increases the safety in driving.
However, when the vehicle moves in the daytime or in a bright environment, it is not necessary to turn on the light-emitting device to serve as lighting and warning means. Moreover, the light emitted from the light-emitting device does not provide significant lighting and warning effects in a bright driving environment. And, the battery cell in the light emitting assembly would have a shortened life when the light-emitting device emits light continuously to consume the battery power all the time.